They've pretty much stated that they don't want too much complexity in this game due to the large number of casual or less skilled people who are playing it.

Personally what bugs me the most is lack of complexity in gear stats, there are no special stats, just the cut and dry base stats with a small handful of substats.

I would love to see some unique stats on gear that do things like improve job abilities, allow you to attack multiple times during auto-attacks, allow you to reflect or mitigate certain types of damage occasionally, the possibilities are pretty much endless and things like this would make gear feel a lot more unique to me.

I would also love to see some expansion to the cross class/job skills, it feels really dumbed down at the moment getting to only pick from a handful of skills for 2 other classes. Combat would be a lot more fun to me if I could actually make semi-hybrid jobs. Obviously there would still have to be key skills that can't be used on an offclass but it almost feels like a nerf when you get your job crystal and lose all of the options available pre-30 to me.